Automatic nut-tapping apparatus

ABSTRACT

A bent tap in a nut-tapping apparatus is provided with an antifriction sliding means arranged in parallel with the tap, which sliding means helps the tap to advance by the lead of its own screw threads during the tapping operation when it is engaged by the bent portion of the tap due to cutting moment.

United States Patent Shinjo [4 1 June 13, 1972 22 Filed:

[54] AUTOMATIC NUT-TAPPING APPARATUS [72] Inventor: Katsumi Shlnio, 8, 6-chome, Asahi Minamidori, Mishinariku, Osakashi, Ja

Jan. 16, 1970 21 Appl. No.: 3,405

[30] Foreign Application Priority Data Jan. 20, 1969 Japan ..44/4607 s2 u.s.c|. ..10/129 [51] Int. Cl .;.B23g 1/04, 823g 1/16 [58] Field oi'Search ..10/129, 129 WH, 129 W];

[56] References Cited UNITED STATES PATENTS 1,217,998 3/1917 Ridlon ..10/129 1,910,090 5/1933 Clouse ..10/129 1,944,653 1/1934 Clouse... .....l0/129 2,201,051 5/1940, Ogilvie ..10/129 FOREIGN PATENTS OR APPLICATIONS 434,063 8/1935 Great Britain..... ..10/ 129 Primary Examiner-Charles W. Lanham Assistant Examiner-E. M. ,Combs Attorney-Arnold Robinson [57] ABSTRACT 4cm, loDrawlngflgures PATENTEDJuuw I972 I r 8.666.726

A I L PATENTEDJUH 13 [are SHEET 2 OF 5 Fig 2 PATENTEDJUH13 I972 3.668 726 sum 5 or 5 AUTOMATIC NUT-TAPPING APPARATUS This invention relates to a nut-tapping apparatus which is adapted to tap nuts automatically, and more particularly, to an automatic nut-tapping apparatus in which nut blanks are successively tapped with precisely cut screw threads on their inside surface.

According to some prior art apparatus of this class a nut is tapped while the bent tap, held in a holder is forcibly fed in its axial direction together with various drive elements, such as cams, springs, weights, levels, or guiding screws; or, altematively, a nut forcibly fed by means of a pusher or the like, has the disadvantage that the axial movement of a bent tap or a nut does not always coincide with the self-advancement of the tap by the lead of its screw threads, which disadvantageously causes a resisting force against the self-advancement of the tap. The resisting force being directed in the axial direction, prevents production of precisely cut threads in a nut.

In addition, in accordance with the self-advancement of the tap, a tapped nut must push all the previously tapped nuts carried on the full length of the shank, including the bent portion, whereby the tap encounters considerable resistance against self-advancement due to a heavy stock of tapped nuts and also the non-straightness of the bent portion of the shank.

Because of this axial resisting force, the screw-thread form in the nuts is quite likely to be deformed particularly in the working surfaces of threads thus leading to inaccurate angles, shapes, and dimensions, and even to wear and premature breakage of taps.

Another disadvantage involved in the prior art is what is known as a hulling phenomenon. This phenomenon results from the structure of the prior art apparatus, wherein the straight-shank portion of a bent tap is in a holder, with tapped nuts carried thereon, which means that the tap is held rigidly. However, in such an apparatus clearances are essentially provided between the holder and the nut and between the nut and the shank of the tap so as to .permit the tapped nuts to move along the shank portion. This clearance causes the tap to fluctuate therein during the cutting operation, resulting in the socalled "hulling phenomenon. On the other hand, the nut to be tapped is liable to the axially directed load pointed out above and is prevented from co-working with the fluctuating tap thus resulting in an enlarged thread hole in the nut.

This invention substantially obviates the drawbacks and disadvantages mentioned above and has for its principle object to provide an apparatus for automatically tapping nuts in a device arranged to ensure non-resistant axial movement of a tap during a thread-cutting operation.

Another object is to effect free passage of tapped nuts along the smooth shank of the tap thereby enabling the apparatus to produce precisely threaded nuts at high speed.

According to this invention, there is provided a rotary guide cylinder having a polygonal hole of a cross-section corresponding with but slightly larger than the profile of a nut blank to be tapped, the nut blank being thus free to move axially through the guide but prevented from rotating therein. A nut guide sleeve is mounted coaxially with said cylinder and has a round hole capable of accepting the nuts carried on the smooth shank of the tap. A tap comprising a cutter portion, a straight-shank, and a bent shank is positioned in the rotary guide and guide sleeve from which the bent shank protrudes and hangs downwardly. As the rotary guide turns, the nut blank slidably held therein is fed along the cutting portion of the tap and thence onto the straight shank portion along which they are pushed by succeeding nuts until they slide off the bent shank portion and into a collector bin. During the actual thread cutting operation the bent shank is caused to swing until its free end engages an anti-friction slider assembly which moves with it during the tapping operation.

The invention will now be particularly described by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a view in front elevation of an apparatus constructed in accordance with the present invention, parts thereof being removed to reveal internal construction.

FIG. 2 is a plan view of the apparatus illustrated in FIG. 1.

Figure 3 is a view in section taken on the line 1-1 in FIG. 2.

FIG. 3a is a view as illustrated in FIG. 3, particularly showing the position of the cutter of the tap when it passes through a cut.

FIG. 4 is a view as illustrated in FIG. 3 and 30, particularly showing the tap in thread-cutting operation.

FIG. 5 is a view in section taken on the line 2-2 in FIG. 3.

FIG. 6 is a view in section taken on the line 3-3 in FIG. 3.

FIG. 7 is a view in section taken on the line 4-4 in FIG. 4.

FIG. 8 is a schematic view showing the screw threads formed in accordance with the prior art.

FIG. 9 is a schematic view showing the screw threads formed in the apparatus of this invention.

The apparatus of this invention includes a frame 10 housing an electric motor 11 and a speed-reducer 12. The speedreducer 12 has an input pulley 13 connected to an output pulley 15 of the motor 11 by means of V-belts l4, and has an output shaft 16 on which is fastened a driving pulley 17.

On the frame 10 is fixed a casing 18 which has a cylindrical boss 19 extruded inside as is apparent in FIG. 3, 3a and 4. A cylindrical holder 20 has a flange 21 at one end and is rotatably supported in the boss 19 by means of roller-bearings 22 and ball-bearings 22 A rotary guide cylinder 23 has an axially extending hexagonal hole 24 which is identical in section to the profile of a nut blank 58 to be tapped. The hole 24 is slightly larger than the nut blank 58 which thereby may be removed axially but not rotatably. The entrance 25, of cylinder 23, is flared outwardly to enable easy entry of the nut blank therein. The cross-sectional shape of the hole 24 may be selectively decided in accordance with the profile of the nut to be tapped.

In the apparatus according to this invention, it is required that the nut blank to be tapped be free to move axially but not rotatably and, accordingly, the nut blank must be at least fourcornered in shape. In the front part of the rotary cylinder 23, there are clearance slits 26 through which lubricants and cutting chips may be discharged.

One end of the rotary cylinder 23 is screwed into the holder 20 from the flange 21 thereby effecting unitary rotation of both members 23 and 20 about the central axis 27. The rotation of cylinder 23 is clockwise when the screw threads are being cut. v

Preferably, a rotary extension guide cylinder 28 is disposed adjacent the rotary cylinder 23, which guide cylinder 28 has a hexagonal hold 29 of the same size and configuration as hold 24 in cylinder 23. Cylinder 28 is screwed into the holder 20 from the opposite direction of the rotary cylinder 23 and is timed so that the flats of holes 24 and 29 form a continuous matching nut guide.

A cup shaped driven pulley 30 is counterbored to fit onto flange 21 of the holder 20, to which it is secured, by means of fastening bolts 32.

The pulley 30 is connected to, and driven by, the driving pulley 17 by means of a flat belt 33 thus causing holder 20, cylinder 23 andcylinder 28 to rotate, as a unit, about the central axis 27 in the desired direction.

A nut guide sleeve 34 has a round axial hole 35 of a diameter slightly larger than the diagonal dimension of the nut. A clearance slot 36 is provided in the lower part of sleeve 34 to clear the bent shank 45 of the tap and finished nuts carried thereon.

A supporting block 37, affixed to the frame 10, has, in its inside surface, a recess 38 to the face of which a mating member 40 is arranged and provided with a recess 39. The guide sleeve 34 is clamped in the recesses 38 and 39 by means of a locking bolt 41 and is thereby adjustable to align it with central axis 27 and adjacent the free end of guide cylinder 28.

A tap 42 consists of a cutter portion 43 and a shank portion consisting of a straight portion 44 and a bent portion 45 extending downwards.

The straight-shank portion 44 carrying tapped nuts 58a thereon is positioned in the hole 35 of the guide sleeve 34. The cutter portion 43 is caused to advance in the hexagonal holes 29 and 24, and, in the meantime, the bent shank portion 45 freely extends downwards from the hole of the sleeve 34 where the angular displacement of the bent shank (FIG. 7) is limited, basically, by a side wall 46 on the supporting block 37.

The side wall 46 is provided with a dovetail groove 47, arranged in parallel with the central axis 27, which has rollers 50, rotatably fitted in retainers 49, against which rollers the slider 48 is slidably mounted.

The bent shank 45 is caused to swing about the central axis 27 towards the side wall 46 by virtue of the cutting moment until its free end comes into engagement with the slider 48 whereupon the slider 48 is caused to move together with the tap 42 in the axial direction. 7

A projecting piece 51 is attached to the slider 48 and is engageable against the bent shank portion 45. The piece 51 is engaged by the bent shank 45 when the latter gravitationally returns to the perpendicular position after the tap 42 has finished a thread-cutting operation. The backward movement of slider 48 is limited by means of a stop 52 attached to the supporting block 37.

The tap 42 can be easily removed by hand from the guide sleeve 34 by swinging the bent shank 45 in the opposite direction to the side wall 46.

The tapped nuts 58a when pushed onto and off the end of the shank 45, gravitate through an opening 53 formed on the frame 10, which opening 53 is in communication with a chute 54 disposed in the frame 10. The chute 54 is mounted in a downward'direction towards a discharge port projecting over a nut-collecting container 57, as is illustrated in FIG. 1. The container 57 is mounted ona base 56 disposed in the front part of the frame 10.

A magazine is disposed adjacent the nut blank receiving end of cylinder 23 to hold a supply of nut blanks. At the lower end of magazine 60 a delivery passageway 61 is provided in such a manner that the lowermost blank 58a is positioned with its hole 59 coaxial with the central axis 27, as illustrated in FIG. 3, 3a and 4.

The nut blanks 58a, in the delivery passageway 61, are pushed seriatim, into the hexagonal hole 24 of the rotary cylinder 23 by means of areciprocable mandrel 62 which is provided with a pin 64, on its end face 63, adapted to enter the holes 59 of the nut blanks 58a which are thereby held in proper alignment with the tap for engagement thereby.

OPERATION The operation of the apparatus will be described, with reference to the example illustrated in the accompanying drawings:

If, as shown in FIG. 4, a quantity of finished nuts 58a has been left on the straight-shank portion 44 of tap 42 after a previous tapping run, a new run may be initiated by simply depositing a supply of nut blanks 58 in magazine 60 and starting the drive motor 1 1.

However, if the tap 42 has been removed from the machine and all the tapped nuts 58a removed therefrom, it must be manually inserted in holes 24, 29 and 35 and properly aligned on axis 27 to receive the first nut blank 58 from magazine 60. This may be accomplished in several ways the most desirable being to run a finished nut up on the taps but not out of engagement with the teeth thereof, inserting the threaded end of the tap and nut thereon through holes 35, 29 and 24 to its normal operative position and finally slipping another nut over the bent shank 45 of the tap to a position just inside of hole 35 in guide alcove 34 after which the machine may be started in the usual manner.

The driving pulley 17 is driven through the speed-reducer 12 by the motor 11, thereby causing the rotary cylinder 23 to rotate about the central axis 27 at high speed. The mandrel 62 is caused, by suitable means (not shown), to drive the lowermostblank through the delivery passageway 61 and into the flared opening of the hexagonal hole 24 of the rotating cylinder 23.

As soon as the nut blank 58a enters the hole 24, it is caused to rotate together with the rotating cylinder 23 and, as it is advanced by the mandrel, it engages the end of the tap 42 (which is consequently advanced) until the bent shank 45 comes into engagement with the projection piece 51, thus causing the slider 48 to move backwards, as shown in FIG. 3a. When the nut blank 58a is advanced in the hole 24 to the position where tap 42 pushes the slider 48 into engagement with the stopper 52, the cutter portion 43 of the tap engages in the nut blank 58a and the tapping operation begins after which the mandrel 62 is caused to retreat.

When the tapping is started in the above manner, the tap 42 is subject to the cutting moment and, as a result, the free end of the bent shank 45 is caused to swing about the axis 27 towards the side wall 46 until it comes in engagement with the slider 48. The slider 48 engaged by the bent shank 45 is caused to slide on the rollers 50 in the axial direction, enabling the tap 42, as a whole, to move axially with minimum frictional resistance thus eliminating axially directed resisting force and thereby producing precisely cut screw threads on the inside I surface of the nuts by virtue of the slider.48, the advancing speed of the tap 42 varies with the varying magnitude of the resisting force.

The significant features of the screw threads produced by the apparatus according to the present invention illustrated in FIG. 9 in comparison with those by the prior art apparatus illustrated in FIG. 8:

FIGS. 8 and 9 show the difference between the screw threads produced by the apparatus of the prior art and of this invention, respectively. Referring to FIG. 8, the inside surface of the nut is cut off by each cutter-thread of the tap, each cut being shown by the reference numeral 65, but each cut 65 is caused to be displaced by the resisting force in the axial direction as is shown in this Figure, in which the broken lines show the sides of a screw thread which would otherwise be produced correctly. The actual side 66a is appreciably displaced, axially, in comparison with the imaginary side illustrated by the broken lines, resulting in an unaccurate threadangle. The other side 66b is repeatedly cut by each cutterthread of the tap and, finally, is displaced at a considerable distance from the imaginary side, which means excessive work for the tap cutter thus resulting in a shortened life of a tap.

On the contrary, in the apparatus according to this invention, a slight displacement of the cut portion is caused due to the resisting force initially brought about when the cutterthreads of the tap engage the inside surface of the nut blank but, in accordance with the gradual removal of it the displacement is corrected, as is shown in FIG. 9, resulting in precisely cut screw threads with proper sides and a prolonged tap life due to reduced work load thereon.

During the tapping operation, the tap 42 is caused to advance by the lead of its own screw. By virtue of the anti-friction slider 48 which is engaged by the bent shank 45, during the tapping operation, a negligible amount of inertia will be exerted on the tap thus facilitating motion of the tap 42 in the axial direction. By the resultant effect of the smooth reciprocation of the tap 42 and the high-speed rotation of the rotary cylinder 23, a number of nuts can be tapped successively at increased speed, which imparts high efficiency to the apparatus of this invention.

As completely tapped nuts run off the end of the tap onto the straight-shank portion 44 thereof, the cutting moment is removed from the tap 42 whereupon the lower free end of bent shank 45 gravitates out of engagement with slider 48 to its original perpendicular position in which the tapped nuts 58a are free to gravitate through the opening 53 and into container 57. I

The pusher 62 is withdrawn during the tapping operation and, immediately after the transfer of a tapped nut to the straight-shank 44 is effected, the pusher 62 is caused to advance and push the next nut blank 58 from magazine 60 through passageway 61 into cylinder 23.

What I claim is:

1. An automatic nut-tapping apparatus comprising a tap (42) embodying a cutter portion (59) and a straight-shank thread-clearing portion (44) bent downwardly at its free end (45), a rotary guide cylinder (23) having internal sidewalls defining a polygonal bore of a cross-section corresponding to the profile of a nut (58) to be tapped, and adapted to hold said nut slidably but not rotatably therein wherein said rotary guide cylinder (23) holds a plurality of tapped nuts (58a) and communicates with a stationary tapped nut guide-sleeve (34), means (1 1-17) for rotating said cylinder (23), said tapped nut guide-sleeve (34) mounted coaxially with said cylinder (23) and having a circular bore adapted to accept said tapped nut (58a) and carry a plurality of said tapped nuts (58a) on said shank (44), said cutter portion (54) of said tap (42) being reciprocally disposed in said rotary cylinder (23) with said straight-shank portion (44) disposed in said guide sleeve (34) and adapted to support tapped nuts slidably thereon, an antifriction slide (48) disposed adjacent and engageable by said free end of said bent shank (45) when said bent shank is caused to swing by cutting moment of a tapping operation whereby said anti-friction slide (48) enables said tap (42) to self-advance axially with minimum resistance and a stop (51) adapted to engage and limit the movement of said tap (42) in a retrogressive direction.

2. The apparatus of claim 1 wherein a guide cylinder (28) having a polygonal bore is provided between and coaxially with said rotary cylinder (23) and said stationary guide sleeve (34), the polygonal bore of said guide cylinder and the polygonal bore of said rotary cylinder being in alignment to form a continuous matching nut guide to said guide sleeve.

3. The apparatus of claim 1 which comprises a supporting block (37) having an inside recess (38), a matching member (40) with facing recess (39) for reception of said guide sleeve (34) and clamping means (41) for securing said guide in said recesses.

4. The apparatus of claim 1 which comprises a storage receiver (57), and a chute (54),.for guiding tapped nuts falling from the free end of bent portion (45) of said tap (42) into said receiver. 

1. An automatic nut-tapping apparatus comprising a tap (42) embodying a cutter portion (59) and a straight-shank threadclearing portion (44) bent downwardly at its free end (45), a rotary guide cylinder (23) having internal sidewalls defining a polygonal bore of a cross-section corresponding to the profile of a nut (58) to be tapped, and adapted to hold said nut slidably but not rotatably therein wherein said rotary guide cylinder (23) holds a plurality of tapped nuts (58a) and communicates with a stationary tapped nut guide-sleeve (34), means (11- 17) for rotating said cylinder (23), said tapped nut guide-sleeve (34) mounted coaxially with said cylinder (23) and having a circular bore adapted to accept said tapped nut (58a) and carry a plurality of said tapped nuts (58a) on said shank (44), said cutter portion (54) of said tap (42) being reciprocally disposed in said rotary cylinder (23) with said straight-shank portion (44) disposed in said guide sleeve (34) and adapted to support tapped nuts slidably thereon, an anti-friction slide (48) disposed adjacent and engageable by said free end of said bent shank (45) when said bent shank is caused to swing by cutting moment of a tapping operation whereby said anti-friction slide (48) enables said tap (42) to self-advance axially with minimum resistance and a stop (51) adapted to engage and limit the movement of said tap (42) in a retrogressive direction.
 2. The apparatus of claim 1 wherein a guide cylinder (28) having a polygonal bore is provided between and coaxially with said rotary cylinder (23) and said stationary guide sleeve (34), the polygonal bore of said guide cylinder and the polygonal bore of said rotary cylinder being in alignment to form a continuous matching nut guide to said guide sleeve.
 3. The apparatus of claim 1 which comprises a supporting block (37) having an inside recess (38), a matching member (40) with facing recess (39) for reception of said guide sleeve (34) and clamping means (41) for securing said guide in said recesses.
 4. The apparatus of claim 1 which comprises a storage receiver (57), and a chute (54), for guiding tapped nuts falling from the free end of bent portion (45) of said tap (42) into said receiver. 